A thermal system is used to elevate the temperature of exhaust gas to activate a selective catalytic reduction (SCR) catalyst in a vehicle exhaust system. The SCR catalyst reduces levels of NOx using ammonia as a reductant. The reducing agent, such as diesel exhaust fluid (DEF) for example, reacts with NOx to convert pollutants into nitrogen and water. Under certain operating conditions, such as cold start conditions, exhaust temperatures are not initially high enough to support efficient operation of the SCR catalyst. This can lead to urea deposit formation from the DEF injection. It is therefore desirable to provide a thermal management system that can ensure that the SCR catalyst is operating efficiently and optimally under all conditions.